1. Field of the Invention
The present invention relates to removable media libraries and more specifically to disaster recovery operations in such libraries.
2. Description of the Prior Art
Removable media libraries are used to store large amounts of computer data. The computer data is typically recorded on a plurality of removable media such as magnetic tape cartridges or optical disk cartridges. The plurality of cartridges are located in a system of storage bins which are accessible by an accessor mechanism, typically a robotic arm. The accessor mechanism moves the cartridges between the storage bins and the drives (tape drives or optical drives) for reading and writing.
Computer data stored on the removable media are typically arranged in data volume units that originally corresponded to the storage capacity of an older original data storage media, such as a reel of tape or tape cartridge or cassette, or an optical disk or cartridge. The capacity of such storage media has grown substantially in recent years. Thus, the average size of data volume units (or files) in most computer or data processing centers is significantly less than the capacity of the current removable media volumes. Most programming support for peripheral data storage is directed at only the original volume units and does not provide a general solution to storing multiple data sets in the same volume.
A virtual tape server (VTS) is a recent development the better utilizes the full capacity of a removable media cartridge (also called a media volume or a physical volume) is to store multiple data volumes (called virtual or logical volumes) on a single physical volume. Data which would have been stored in multiple, mostly unused physical volumes are collected and stored on a single physical volume in separately addressable, host-processor defined logical data storage volumes. As a result, the host processor treats logical volumes as though they were separate physical media volumes, and the library manages the access to the logical volumes by accessing the associated physical volumes. A subsystem providing automatic management of data storage having such logical volumes is called a virtual tape server. A library system may have multiple virtual tape server partitions and non-VTS partitions which are coordinated by a single library manager.
In order to manage the data within the library system, the various components of the system must contain database mapping information in their memories. This includes such information as the location of the physical volumes within the storage bins, which logical volumes correspond with which physical volumes, which virtual tape servers correspond to which physical volumes, etc. These databases are critical for operation of the library system. If one or more of these database maps is lost, then the system must have a way of reconstructing the databases in order for operation to proceed.
Current state of the art requires a lengthy and disruptive method for identifying removable media as disaster recovery volumes as part of a disaster recovery operation. The current method requires that the entire removable media library be made unavailable to all hosts, all removable media in the library must be scanned, and the library controller database must be reconstructed.
Briefly, in a preferred embodiment, the present invention comprises two new methods for identifying removable media as disaster recovery volumes as part of a disaster recovery operation comprising the steps of:
selecting a virtual tape server (VTS) to perform disaster recovery upon;
selecting to perform disaster recovery using a partial inventory method;
selecting which frames to perform the partial inventory upon;
scanning all removable media only in the selected frames;
adding newly scanned volume VOLSERS to the library controller database;
associating, via VOLSER range tables, the removable media with the appropriate VTS;
identifying the volumes associated with the VTS being recovered as disaster recovery volumes;
proceeding with the disaster recovery process which includes identifying the removable media volume with the most recent VTS database backup by mounting each volume identified as a disaster recovery volume and reading the timestamp of the database backup and subsequently mounting the most recent volume and recovering the VTS database from the volume; or alternatively,
selecting a virtual tape server (VTS) to perform disaster recovery upon;
selecting to perform disaster recovery using an automatic method;
identifying the volumes associated with the VTS being recovered as disaster recovery volumes using program code;
proceeding with the disaster recovery process which includes identifying the removable media volume with the most recent VTS database backup by mounting each volume identified as a disaster recovery volume and reading the timestamp of the database backup and subsequently mounting the most recent volume and recovering the VTS database from the volume.